It's Chef Mustafa San's secret sauce. Of which his fans who know the guy as a master of Middle Eastern munchies from his stints at Tempe's Efes Turkish Cuisine and now Mill Avenue's Med Fresh Grill are quite familiar. The Anatolian edibles at Med Fresh are some of the best and least expensive of their kind in town: kebab, baklava, falafel, you name it. But we're hooked on his sauce, and slather it on everything pita, rice, meat, everything. Crikey, we'd eat a dachshund if it was dipped in the stuff. The recipe? Mustafa's not sharing. You can guess all you want. He'll even let you take some home for further, um, analysis. But there's only one way to acquire this savory spread, at the Med Fresh Grill, and the cagey Mustafa plans to keep it that way.